A brake fluid pressure control device for vehicle described in Patent Literature 1 includes a wheel cylinder serving as an example of a control target disposed on a wheel, an electromagnetic valve connected to the wheel cylinder through a flow path in which a brake fluid flows, and a control unit controlling a degree of opening of the electromagnetic valve by PWM control. The “PWM” is an abbreviation of “Pulse Width Modulation”.
Note that the electromagnetic valve has a valve seat, a valve element that can reciprocally move in a direction approaching the valve seat and in a direction away from the valve seat, a solenoid in which a current having a magnitude depending on a control signal from the control unit flows. In the electromagnetic valve, electromagnetic force is generated depending on the current flowing in the solenoid to adjust the width of a spacing between the valve seat and the valve element, i.e., a degree of opening.
In the brake fluid pressure control device, under the situation in which the electromagnetic valve is controlled within a range in which the valve element is not seated on the valve seat, when the brake fluid flows in the electromagnetic valve through the flow path, the valve element of the electromagnetic valve may cause self-excited vibration. When the self-excited vibration occurs in the electromagnetic valve, abnormal noise is generated from the brake fluid pressure control device, and an occupant of the vehicle may feel uncomfortable.
Thus, in the brake fluid pressure control device described in Patent Literature 1, when occurrence of self-excited vibration in the electromagnetic valve is predicted, a frequency of a control signal to be input to the electromagnetic valve is set to be higher than a frequency in a normal state. Therefore, the self-excited vibration does not easily occur in the electromagnetic valve to suppress generation of abnormal noise caused by the self-excited vibration in the electromagnetic valve.